You can also try to find a comic by Lou Kagan called "the Lair of Lady Lovelock" I've only found a handful of pics and the book seems to be out of print.

There is a site called IDG (innocent dick girls). Pretty hot comic site. The art work is inconsistent but a lot of it is pretty hot. The intro talks about how they became dick girls (futanari might be more acurate - most of them seem to have both anatomies). I don't know if they actually show it.